1. Field of the Invention
This invention generally relates to an ink-jet printer, and, in particular, to an encased ink-jet printer head unit having a substantially enclosed structure. More specifically, the present invention relates to an encased print head unit suitable for use in an ink-jet printer of the type in which a series of charged ink droplets are passed through an electric field which is modulated by an image to be recorded.
2. Description of the Prior Art
An ink-jet printer is well-known in the art and one example of a prior art ink-jet printer is shown schematically in FIG. 5. The ink-jet printer shown in FIG. 5 is the so-called charged ink droplet deflection type ink-jet printer in which a series of charged ink droplets are passed through an electric field whose strength is modulated by an image to be recorded to thereby cause the charged ink droplets to be deflected selectively in accordance with image information to be recorded. As shown in FIG. 5, the charged ink droplet deflection type ink-jet printer includes a carriage 1, and a print head 4, from which a series of ink droplet are ejected, is mounted on the carriage 1 via a pair of first and second adjusting plates 2 and 3. A pair of top and bottom deflection electrodes 5 and 6 spaced apart from each other vertically is disposed in front of the print head 4. A gutter 1a for collecting non-deflected ink droplets is integrally formed with the carriage 1. The first adjusting plate 2 is mounted on a horizontal section 1b of the carriage 1 such that it can be adjusted in angular orientation on the horizontal section 1b of the carriage by means of an off-center screw 7. On the other hand, the second adjusting plate 3 is generally L-shaped and pivotally supported by a pair of horizontal pins 8 and it is normally spring-biased to have a tendency to rotate around the pins 8 in the clockwise direction. An adjusting screw 9 extends through a hole formed in the second adjusting plate 3 and determines the angular position of the second adjusting plate 3 around the pins 8. With this structure, the ink droplet ejecting direction by the head 4 may be adjusted not only in the horizontal direction but also in the vertical direction.
In operation, a series of ink droplets are ejected from the head 4 forwardly and they fly through the gap between the top and bottom deflection electrodes 5 and 6, between which an electric field may be formed. Although not shown in FIG. 5, a charging ring is normally disposed at or near the exit of the head 4 so that a series of ink droplets ejected from the head 4 are charged to a predetermined level. If no image information is supplied, the charged ink droplets fly along the gap between the top and bottom deflection electrodes 5 and 6 to be collected into the gutter 1a. In this instance, an electric field may be present between the top and bottom electrodes 5 and 6, but the electric field strength is weak enough to cause the ink droplets to be collected into the gutter 1a. On the other hand, when image information to be recorded is supplied, the strength of the electric field formed between the top and bottom electrodes 5 and 6 is modulated in accordance with the image information thus supplied, so that the charged ink droplets flying along the gap between the top and bottom electrodes 5 and 6 are deflected selectively, whereby the magnitude of deflection depends on the level of electric field intensity. The thus deflected ink droplets are not captured by the gutter 1a, but they fly past the gutter 1a to land on a sheet of recording paper placed opposite to the print head 4. In this manner, ink-jet recording can be carried out.
However, with the prior art ink-jet printer shown in FIG. 5, ink may fall onto the carriage 1 for some reason, for example, overflowing from the print head 4, and such spilled over ink may be scattered around, thereby causing various problems, such as smearing and shorting of printed circuit boards typically incorporated in such a printer, though not shown specifically. Besides, it was often the case that the print head 4 became disoriented after using for a while. In such a case, attendance of a skilled service personnel was required because the adjustments in orientation of the print head 4 was a delicate task so as to obtain a fine printing quality.